Magnetic setback-centrifugal switch

ABSTRACT

THIS INVENTION RELATES TO A MAGNETIC SETBACK-CENTRIFUGAL SWITCH FOR SIMULTANEOUSLY CLOSING A PLURALITY OF CIRCUITS IN A SPIN STABILIZED PROJECTILE AFTER IT HAS BEEN LAUNCHED. THE DEVICE UTILIZES A HOUSING MEANS, A PRINTED CIRCUIT MEANS OPERATIVELY POSITIONED IN THE HOUSING, A FIXED MAGNET MEANS OPERATIVELY POSITIONED INTERMEDIATE TO THE HOUSING AND THE PRINTED CIRCUIT MEANS, AND AN INERTIAL POLE MEANS MAGNETICALLY HELD ADJACENT TO THE FIXED MAGNET AND SLIDABLY REMOVABLE THEREFROM THE SEQUENTIALLY APPLIED LINEAR AND ANGULAR ACCELERATING FORCES CAUSED BY SETBACK AND SPIN OF THE PROJECTILE.

S. LEVINE Feb. 27, 1973 MAGNETIC SETBACK-CENTRIFUGAL SWITCH 2 Sheots-Shoot 1 Filed Dec. 4., 1971 Feb. 27, 1973 vl 3,718,787

MAGNETIC SETBACK-CENTRIFUGAL SWITCH Filed Dec. 4, 1971 2 Sheets-Sheet 2 FIG. 2

3 718 7 87 MAGNETIC SETBACK-CENTRIFUGAL SWITCH Seymour Levine, Dover, N.J., assignor to the United States of America as represented by the Secretary of the Filed Dec. 4, 1971, Ser. No. 204,223 Int. Cl. H01h 35/10 US. Cl. 20080 Claims ABSTRACT OF THE DISCLOSURE This invention relates to a magnetic setback-centrifugal switch for simultaneously closing a plurality of circuits in a spin stabilized projectile after it has been launched. The device utilizes a housing means, a printed circuit means operatively positioned in the housing, a fixed magnet means operatively positioned intermediate to the housing and the printed circuit means, and an inertial pole means magnetically held adjacent to the fixed magnet and slidably removable therefrom by the sequentially applied linear and angular accelerating forces caused by setback and spin of the projectile.

The invention described herein may be manufactured, used and licensed by or for the Government for governmental purposes without the payment to me of any royalty thereon.

BACKGROUND OF THE INVENTION Various means have been used in prior art to make a missile safe during the launch operations, armed during its flight and impact stage, and once again safe in the event that the missile did not function upon impact. The means used for performing these functions have been accomplished by a variety of mechanical, electrical, chemical devices, and a combination of these three to produce a safe device for the handling personnel during launch and for the personnel assigned to clearing an area which contains missiles which failed to function. Some of the prior art devices which utilize mechanical-electrical combinations to perform electrical switching functions initiated by linear acceleration or setback and the centrifugal forces generated by the spin of the missile, are expensive, large in size and unreliable because of their dependence upon complicated mechanical elements. The size and reliability problems are particularly acute where it is desirable that several circuits be switched simultaneously. Some prior art devices that are inertially actuated to close an electrical switch are dependent upon a spring loaded weight responsive to the setback and spin forces. Other prior art devices utilize spring loaded stacked wafer type switches with multiple contacts thereon. The latter type is generally inferior to the present invention because of the larger size and the dependency upon an extrinsic timing mechanism.

Prior art devices are generally less satisfactory than the present device because they are larger in size and less reliable because of a dependency upon springs to restrain the pole means in the safe position.

SUMMARY OF THE INVENTION The present device relates to an electric switch which may be utilized to maintain a missile in a safe condition during the launch phase and in an armed operative condition after its firing. The present invention provides for a redundancy in multiple switching which is reliably responsive to sequentially applied prior linear acceleration and subsequently applied angular acceleration. The present device is capable of switching a minimum of 5 re- United States Patent 0 "ice dundant circuits in a switch volume of less than one cubic inch.

In accordance with the present invention a permanent magnet is used to hold two pairs of diametrically positioned magnetic pole pieces so that integral contacts mounted thereon are maintained in a position which will keep a series of redundant ciricuits and contacts in an open circuit position when the missile is unfired. The permanent magnet and the magnetic pole pieces are contained within a housing which also holds a printed circuit board which has mounted therein redundant circuits having open integral contacts which fit within the housing and are positioned opposite from the movable pole pieces. A flat connection cable is attached to the printed circuit board and passes through the housing, thereby providing electrical connections to the internal connections mounted on the printed circuit board. The magnetic pole pieces upon receiving the proper linear and centrifugal accelerating forces make contact with the printed circuits and close the circuits contained thereon. The printed circuits are series and parallel connected so that either pair of diametrically positioned pole pieces are required to close in order to complete the circuit. The housing is so designed that inadvertent dropping of the missile will not cause the pole pieces to close the printed circuit contacts. The sensitivity of the device can be varied readily by changing the strength of the magnetic holding magnets and the permeance of the pole means.

One of the objects of this invention is to provide an electrical switch which will close a multiplicity of circuits upon receiving sequential linear and angular accelerations.

Another object of this invention is to insure reliable switching of multiple circuits by having at least two set of pole means responsive to the same actuating forces.

Another object of this invention is to provide a magnetically held pole means which is actuated only by sequential linear and angular acceleration forces.

Another object of this invention is to provide a device for redundancy of switching of a plurality of electrical circuits by the setback and spin forces of a missile in a switch volume of less than one cubic inch.

Another object of this invention is to provide a device for reliable multiple switching in a device which is operable under 15,000 G linear acceleration and 10,000 G of angular acceleration.

For a better understanding of the present invention, together with other and further objects, reference is made to the following description taken in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an exploded and partial cross-sectional view of the setback-centrifugal switch.

FIG. 2 is a perspective and cross-sectional view of the setback-centrifugal switch illustrated in FIG. 1.

Throughout the following description like reference numerals are used to denote like parts of the drawing.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is concerned with a device which will reliably and redundantly effect the multiple closure of several circuits when the invention is subjected to a linear and sequential angular accelerating force. The device is intended for use in a projectile to prevent arming and possible malfunction during the launch stages, and to automatically arm the projectile by simultaneously energizing a multiplicity of redundant electrical circuits after the launching. The present device is so constructed that in the event the missile does not destruct after launch the magnetic pole means will automatically return the 3 electrical connections to the open circuit condition and the missile to the safe mode.

Referring now to FIGS. 1 and 2 a cylindrical housing base has an open end 12 and a closed end 13. Base 10 is made of a non-magnetic insulator type material such as Lexan. The housing base 10 has a cross recess therein forming four rectangular L-shaped cavities 11, 11a, 11b and 110, respectively.

A printed circuit wiring board has a flat integrally attached flexible cable 21 which has embedded therein electrical conductors 22 and four electrical contact surfaces 23, 23a, 23b and 230 which slidably fit immediately adjacent to the inner back wall surface 11', 11a, 11b and 110 of the L-shaped cavities 11, 11a, 11b and 110, respectively.

The four electrical contact surfaces 23, 23a, 23b and 230 have embedded therein printed circuit wiring having pairs of terminations such as 24, 25 operatively positioned so that they will be either electrically open or closed circuited when the pole means is actuated by the proper accelerating forces. The printed circuit board 20 has a cross-shaped orifice 26 therein which is of the same size and symmetrically aligned with the cross-shaped orifice 14 in the open end 12 of the housing base 10.

The four U-shaped inertial ceramic pole magnets 30, 30a, 30b and 300 have multiple electrical shorting contacts 31, 31a, 31b, 31c and 31a operatively mounted on the inside magnet surfaces 35, 35a, 35b and 350. The electrical shorting contacts 31, 31a, 31b, 31c and 310. each have flexible fiat metal end terminations such as illustrated by 32 and 32a. These flexible end terminations insure good contact closure even though there is minor variation in size of either the printed circuit wiring terminations 24 and 25 or in the distance that the flexible tips of the electrical shorting contacts protrude. The electrical shorting contacts 31-31d are electrically isolated from each other by the relatively high resistivity of the ceramic magnet material used in the U-shaped pole means. A rectangular shaped magnet is positioned adjacent to a disc magnet and permanently fixed to each other so that in cross section, as shown in FIG. 2, they form a symmetrical T-shaped fixed magnet. The magnetic north surface 41 of the rectangular magnet 40 is positioned adjacent to the magnetic north surface 51 of the disc magnet 50. The magnetic south surfaces 42 and S2 of the respective aforementioned magnets are positioned furthermost from each other. This will result in attracting parts 30, 30a, 30b and 300 to the corner of the T.

A housing cover has a disc magnet bore 61 and an axially aligned pole means housing bore 62 of slightly larger size.

In operation the closed end 65 of cover 60 is positioned in the direction of the projectile flight. The device is mounted so that its cylindrical axis is axially aligned with the longitudinal axis of the projectile (not shown). When no accelerating forces are present the U-shaped pole pieces are drawn by magnetic attraction to the position as shown in FIG. 2. In this position the electric contact pairs as illustrated by printed circuit terminations 24 and 25 on the printed circuit board 20 are maintained in an open position. For safety purposes the printed circuit board 20 is designed so that both pairs of diametrically opposed pole means 30, 30a and 30b, 300 have to move radially outward to complete the circuit. When redundancy is required for reliability either of the two pairs of inertial magnetic pole means may be connected in parallel so that the circuit closure will be effected even though only one pair of the inertial pole means properly functions. When the device receives a linear acceleration, such as that caused by the set-back forces when the projectile is launched from a weapon, the four U-shaped magnetic inertial masses are caused to move by the setback force from the open housing end 12 toward the closed housing end 13. The legs 33, 33a, 33b and 330 of the inertial masses move off the inner wall 63 of the disc magnet housing bore 61. The aforementioned legs 33, 33a, 33b and 330 upon clearing the inner wall 63 of the disc housing bore 61 move radially outward toward pole means housing bore inner wall 64 and the legs 34, 34a, 34b and 3540 move into foot sections 15 (not shown), 15a, 15b and 150 of the housing cross-cavity L-shaped cavities 11, 11a, 11b and 11c, when the inertial pole means masses are subject to the centrifugal forces created by the spin of the projectile. The inertial pole mean masses will maintain a closed switch condition only so long as the centrifugal environment exists. Whenever the centrifugal and linear accelerating environments cease to exist the masses will be attracted back to their rest position as shown in FIG. 2.

I wish it to be understood that I do not desire to be limited to the exact method and detail of construction described for obvious modification will occur to persons skilled in the art.

What is claimed is:

1. A magnetic setback-centrifugal switch for simultaneously closing a multiplicity of circuits comprising:

a housing;

contact means operatively positioned in said housing;

a fixed magnet means intermediate to said contact means and said housing; and

an inertial pole means magnetically held adjacent to said fixed magnet, shorting said contact means and slidably removable therefrom by sequentially applied linear and angular accelerating forces.

2. A switch as recited in claim 1 wherein said housing further includes a plurality of bores for limiting the movement of said pole means so that it responds initially to a linear force and a subsequent angular accelerating force.

3. A switch as recited in claim 2 wherein said contact means comprises:

a printed circuit having a plurality of terminals appended thereto; and

a cable, integrally molded to one side of said circuit having electrical conductors isolated therein and connected to said terminals.

4. A switch as recited in claim 3 wherein said fixed magnet means comprises:

a disc shaped magnet having a magnetic north face surface and a magnetic south face surface; and

a rectangular shaped magnet having a magnetic north end and a magnetic south end, wherein said magnetic north end is atfixed to said magnetic north face surface so that it is perpendicular and symmetrical to said disc magnet.

5. A switch as recited in claim 4 wherein said inertial pole means comprises:

a plurality of U-shaped ceramic magnets, slidably positioned intermediate to said fixed magnetic means and said printed circuit means, having a plurality of electrical shorting contacts mounted on an inner surface of said U-shaped ceramic for shorting said terminals when said switch is subject to sequentially applied linear and angular acceleration.

References Cited UNITED STATES PATENTS 3,194,914 7/1965 Brown 200 R HERMAN J. HOHAUSER, Primary Examiner US. Cl. X.R. 20061.46; 10 270.2, 8O 

